A large class of non-zonal oceanic flows satisfying the arnold-blumen sufficient condition for stability

Abstract

Recently Andrews has discussed an example of a topographically-forced non-zonal now satisfying the Arnold-Blumen sufficient condition for stability. At large distances from the topographic centre this flow becomes purely zonal and westward. After underlining the richness of solutions of the Andrews model, the present paper goes on to show that Andrews' technique can be applied successfully to a model where the vertical profile of static stability resembles those found in the ocean. In particular we obtain a large class of hydrodynamic stable flows, forced by the bottom topography, for continuously stratified fluids (two layers each with uniform Brunt-Väisälä frequency).     

Redevelopment and the urban forest: A study of tree removal and retention during demolition activities

Though relationships between urbanization and tree cover are generally well studied, the effect of redevelopment on urban trees, at the scale of the individual property, is not well understood. Developing knowledge in this area is important in order to limit tree loss during redevelopment and thus, ensure sustained ecosystem services. Here, we explore the removal or retention of trees adjacent to building demolition in Christchurch, New Zealand. We mapped the presence or absence of individual trees on 123 properties prior to, and following, building demolition. Using a classification tree (CT) analysis, the presence or absence of 1209 trees was modelled as a function of: tree-related variables, property-related variables, and economic variables. The CT model estimated tree presence/absence with overall accuracy of 80.4%. Results show that 21.6% of all trees were removed as a consequence of building demolition, resulting in a tree canopy cover reduction of 19.7% across all 123 properties. The CT showed that tree crown area was the most important variable for predicting the presence/absence of trees, whereby trees with small crown areas (<7.9 m²) were most frequently removed, especially if they were within 0.7 m of a demolished building. Land value was also an important determinant of tree presence/absence, such that tree removal was more prevalent on properties with higher land value ($/m²). The results provide important new insights into some of the reasons for tree removal or retention during redevelopment at the scale of the individual property where most tree-related decisions are made.     

The Alleret maar (Massif Central, France): A new lacustrine sequence of the early Middle Pleistocene in western Europe

The Alleret maar (Massif Central, France) provides a long lacustrine sequence (40.6 m) attributed to the early Middle Pleistocene. Sediment, pollen and diatoms analysis of its upper part (AL2 core, 14.6 m) indicates two temperate phases marked by high lake levels, forest development and vegetation expansion. They are separated by a cold period during which lake level drops, coarse sediment input increases and steppic and xerophilous plants develop. Pollen data suggests that this sequence belongs to the upper part of the Cromerian complex. These results are in agreement with the 557 ± 3 ka (±12 ka, including all errors) ⁴⁰Ar/³⁹Ar age obtained from an interbedded tephra layer emitted by the Mont-Dore/Sancy strato-volcano and establish that this sequence probably covers the MIS 15 substages.     

正常小儿颅内不同组织CT值

正常小儿脑组织ＣＴ值国内尚我报告；作者选择１０岁以内正常小儿子１２０例，分三人年龄组进行颅内不同脑组织ＣＴ值测定，并将小儿与成人的脑绰组织值ＣＴ比较，收结果看出；小儿灰质、白质及小脑ＣＴ值明显低于成人的，随年龄增长ＣＴ值递增；新生儿脑组织ＣＴ值明显低于儿童；儿童丘脑莫过基底节ＣＴ值近似成人。     

CHINA''S REGIONAL DEVELOPMENT IN THE 1980s

l.Introducti0nIntheseveraldecadestilltheendofthe1970s,therewasnoanyleastd0ubtthatChinahadbeenfollOwingabalancedregi0naldevelopmentstrategy.0bligedtotlledolnesticandinternationalsituationofthattime,capitalinvestlnentxvasn1ost1yf0rcedt0beputintotheundevel0pedarea(westeconomiczone),thisstrategyprovedtobelesseffectiveandincurredahugelossofinvestmentbenefit.Althoughthewestzoneisabundantinnatllralresources(mineral,energyresourcesetc.),thelevelofregionaldevel0pmentfromeastzonet0westzoneisgradua1lydec…     

脑囊虫病的CT诊断－附300例分析

作者报告了３００例脑囊虫。对脑囊虫病的ＣＴ表现进行了讨论。作者认为；（１）平扫为多发小囊状低密度灶，如囊壁上有高密度点。（２）较大囊状低密度灶，囊壁上有高密度点。（３）平扫为多发局灶性低密度区，增强出现多发结节及环形强化灶。为诊断脑囊虫病有价值的征象。本文还对脑囊虫病的病理及鉴别诊断进行了讨论。     

论γ射线的点放射源和非点放射源的辐射研究

本文讨论点放射源和非点放射源的辐射，为简化理论模型，暂不考虑二次γ射线，只讨论点源和线源和柱状源的辐射，本文的讨论有助于工业ＣＴ的设计及系统的优化。     

Orbital evolution of Uranus’s new outer satellites

Data on three recently discovered satellites of Uranus are used to determine basic evolutional parameters of their orbits: the extreme eccentricities and inclinations, as well as the circulation periods of the pericenter arguments and of the longitudes of the ascending nodes. The evolution is mainly investigated by analytically solving Hill’s double-averaged problem for the Uranus-Sun-satellite system, in which Uranus’s orbital eccentricity e _U and inclination i _U to the ecliptic are assumed to be zero. For the real model of Uranus’s evolving orbit with e _U≠0 and i _U≠0, we refine the evolutional parameters of the satellite orbits by numerically integrating the averaged system. Having analyzed the configuration and dynamics of the orbits of Uranus’s five outer satellites, we have revealed the possibility of their mutual crossings and obtained approximate temporal estimates.     

不同围压下岩石中泊松比的各向异性

由弹性波纵横波速比计算得到的泊松比,在利用地震波反演地下结构和物质组成时,可以提供比单纯地利用纵波或者横波波速更强的约束. 为了研究不同岩石中泊松比及其各向异性随围压的变化,选取19块典型的岩石样品,在不同围压下沿相互正交的3个方向同时测量纵、横波速度,并通过计算得到了泊松比及其各向异性. 结果表明,在大部分样品中泊松比各向异性与纵波速度各向异性有一定的相关性,但在有的样品中泊松比各向异性与纵波速度各向异性没有明显的关系,甚至表现出完全相反的变化规律. 由于泊松比也表现出很强的各向异性,在排除微裂隙的影响后有的仍可以达到30髎以上,在利用实际地震波传播数据通过泊松比反演地下物质结构时必须考虑其各向异性的影响.     

PDCA循环法用于专业硕士产教融合培养模式研究

为满足新时代对卓越工程技术人才的需求,本文在分析专业硕士培养现状基础上,从人才培养方案入手,提出了PDCA理念用于产教深度融合培养模式,讨论了产教深度融合培养的目标制定、计划落实、课程体系开发、导师团队优化及实践基地的质量保障建设等方面的模式与对策,论述了专业硕士研究生培养的质量监控体系,总结出教育教学各环节的计划、执...